Fixed type constant velocity universal joint
A fixed type constant velocity universal joint comprising an outer joint member (1) having eight arcuate guide grooves (1b) extending in the axial direction in an inner spherical surface (1a), an inner joint member (2) having eight arcuate guide grooves (2b) extending in the axial direction in an outer spherical surface (2a), eight balls (3) disposed between the guide grooves (1b) of the outer joint member (1) and guide grooves (2b) of the inner joint member (2), and a cage (4) interposed between the outer and inner joint members (1) and (2) for retaining the balls (3), in which center (P) of guide grooves (1b) of the outer joint member (1) is offset from center (O) of inner spherical surface (1a), and center (Q) of guide grooves (2b) of the inner joint member (2) is offset from center (O) of outer spherical surface (2a) by equal distance (PO=QO=F) to opposite sides in the axial direction, and the relation of 0.45≦B/A≦0.65 is established, where A stands for the wall thickness of the cage (4), and B the radial displacement of balls 3 at maximum joint angle.
1. Field of the Invention
The present invention relates to a constant velocity universal joint used in power transmission in automobiles and various industrial machines, and more particularly to a fixed type constant velocity universal joint having eight balls.
2. Prior Art
Constant velocity universal joints are classified into a fixed type not sliding in the axial direction, and a slidable type.
Centers P and Q of the guide grooves 11b and 12b are offset from the joint center O by an equal distance (PO=PQ) to the right and left side in the axial direction. That is, the center P of guide groove 11b of the outer ring 11 is offset from center O of the inner spherical surface 11a to the opening side of the outer ring 11 by distance PO. The center Q of guide groove 12b of the inner ring 12 is offset from center O of the outer spherical surface 12a to the inner side of the outer ring 11 by distance QO. The centers of inner spherical surface 11a of the outer ring 11 and outer spherical surface 12a of the inner ring 12 coincide with the joint center O.
One (not shown) of two shafts to be coupled is connected to the outer ring 11, and other (shaft part 15) is connected to the inner ring 12. Accordingly, the inner ring 12 has a tooth profile, i.e. serration or spline, 12c to be coupled with the shaft part 15. The outer ring 11 and inner ring 12 form a certain angle, and the balls 13 guided in the cage 14 are maintained within a plane perpendicular to a bisector of angle θ formed by the outer and inner ring 11 and 12, so that the constant velocity of the joint is assured.
In a fixed type constant velocity universal joint, hitherto, a constant velocity universal joint applicable to high angle (maximum joint angle 50°) was an undercut-free joint (called UJ type) comprising six balls 13, but by increasing the number of balls and reducing the ball diameter, a more compact UJ type having eight balls with same strength and durability has been developed (for example, see Japanese Patent Application laid-open under No. H9-317784).
SUMMARY OF THE INVENTION In a fixed type constant velocity universal joint, when torque is transmitted in a state of forming a working angle, in the cage pockets, the balls move in the circumferential direction, and also move in the radial direction at the same time (see
In the fixed type constant velocity universal joint of eight torque transmission balls realizing a more compact design and lighter weight, it is important that the strength at high joint angle should be kept same as that of the conventional constant velocity universal joint of six balls. To increase the strength of the cage, it is easy to increasing the wall thickness of the cage, but by increasing the thickness of the cage, the depth of the guide grooves of the outer and inner rings becomes shallower. As the guide grooves of the outer and inner rings become shallow, contact ellipses of balls can ride over the guide grooves at high angle and high torque load, and the durability life is lowered.
It is hence an object of the invention to present a fixed type constant velocity universal joint of eight balls capable of satisfying two important functions, that is, assurance of cage strength at high angle and assurance of durability life at high angle and high torque load.
It is other object of the invention to present a fixed type constant velocity universal joint of eight balls seeking the optimum thickness of cage in order to have the cage strength at high angle and durability life at high angle and high load equivalent to that of the conventional fixed type constant velocity universal joint of six balls.
It is one aspect of the invention to present a fixed type constant velocity universal joint comprising an outer joint member having eight arcuate guide grooves extending in the axial direction in an inner spherical surface, an inner joint member having eight arcuate guide grooves extending in the axial direction in an outer spherical surface, eight balls disposed between the guide grooves of the outer joint member and guide grooves of the inner joint member, and a cage interposed between the outer joint member and inner joint member for retaining the balls, in which center of guide grooves of the outer joint member is offset from center of inner spherical surface, and center of guide grooves of the inner joint member is offset from center of outer spherical surface by equal distance to opposite sides in the axial direction, and the relation of 0.45≦B/A≦0.65 is established, where A stands for the wall thickness of the cage, and B the radial displacement of balls at maximum joint angle.
It is other aspect of the invention to present a fixed type constant velocity universal joint comprising an outer joint member having eight arcuate guide grooves extending in the axial direction in an inner spherical surface, an inner joint member having eight arcuate guide grooves extending in the axial direction in an outer spherical surface, eight balls disposed between the guide grooves of the outer joint member and guide grooves of the inner joint member, and a cage interposed between the outer joint member and inner joint member for retaining the balls, in which center of guide grooves of the outer joint member is offset from center of inner spherical surface, and center of guide grooves of the inner joint member from center of outer spherical surface, by equal distance to opposite sides in the axial direction, and inner spherical surface of the cage is offset from outer spherical surface thereof to the opposite side by equal distance in the axial direction, and further straight portions having straight groove bottoms are provided in guide grooves of the outer joint member and inner joint member, and the relation of 0.65≦B/A≦0.85 is established, where A stans for the wall thickness of the cage, and B the radial displacement of balls at maximum joint angle.
Value R1 of ratio (F/PCR) of offset amount F to length PCR of line segment linking center of guide grooves of the outer joint member or center of guide grooves of the inner joint member and center of balls may be specified in a range of 0.069≦R1≦0.121.
Contact angle α of guide grooves and balls may preferably be in a range of 29° to 40°. When the offset amount F is decreased, the inversion start angle of wedge angle between guide grooves of the outer joint member and inner joint member becomes smaller, and when the wedge angle is inverted, the play of the balls in the guide grooves is increased, and hammering sound can be generated. Accordingly, to set the wedge angle inversion start angle at least more than the ordinary angle of vehicle or the like, the contact angle α of guide grooves and balls is set in a range 29° to 40°. Herein, the wedge angle refers to the angle formed by a common normal of load side contact point of balls and guide grooves of outer joint member, and a common normal of load side contact point of balls and guide grooves of inner joint member. The ordinary angle of vehicle is generally 9° or less. As the joint angle increases, the wedge angle comes to the minus side going down below zero. This change of sign of wedge angle below zero is called inversion of wedge angle.
The following table shows the relation of the value R1 of ratio (F/PCR) of offset amount F to length PCR of line segment linking center of guide grooves of the outer joint member or center of guide grooves of the inner joint member and center of balls, contact angle α, and wedge angle inversion start angle.
As known from Table 1, the smaller the contact angle α, the larger becomes the wedge angle inversion start angle. Also, the larger the offset amount F, the larger becomes the wedge angle inversion start angle. Therefore, as in the configuration described above, by setting the value R1 of ratio (F/PCR) of offset amount F to length PCR of line segment linking center of guide grooves of the outer joint member or center of guide grooves of the inner joint member and center of balls in a range of 0.069≦R1≦0.121, and specifying the contact angle α of guide grooves and balls in a range of 29 degrees to 40 degrees, the contact ellipse of balls will not be dislocated from the guide grooves to ride over the spherical surface, and at least at the joint angle smaller than the ordinary joint angle of vehicle, play of balls in the guide grooves is eliminated, generation of hammering sound is prevented.
The fixed type constant velocity universal joint of the invention assures the specified thickness of the cage, and realizes a more lightweight and compact structure while having the durability life and high angle strength equivalent to that of the conventional fixed type constant velocity universal joint of six balls.
Referring now to the drawings, preferred embodiments of the invention will be described.
BRIEF DESCRIPTION OF THE DRAWINGS
First, an embodiment of BJ type shown in
As shown in
In this embodiment, centers P and Q of the guide grooves 1b and 2b are respectively offset from joint center O by equal distance (PO=QO=F) to the right and left side in the axial direction. That is, the center (outer ring track center) P of guide grooves 1b of the outer ring 1 is offset from the center O of the inner spherical surface 1a to the opening side of the outer ring 1 by distance PO. The center (inner ring track center) Q of guide grooves 2b of the inner ring 2 is offset from the center O of the outer spherical surface 2a to the inner side of the outer ring 1 by distance QO. The center of the outer spherical surface 4a of the cage 4, and the center of the inner spherical surface 1a of the outer ring 1 as the guide surface of the outer spherical surface 4a of the cage 4 both coincide with the joint center O. Similarly, the center of the inner spherical surface 4b of the cage 4, and the center of the outer spherical surface 2a of the inner ring 1 as the guide surface of the inner spherical surface 4b of the cage 4 both coincide with the joint center O. Therefore, the offset amount (PO=F) of the outer ring 1 is the axial distance between the center P of the guide grooves 1b and the joint center O, and the offset amount (QO=F) of the inner ring 2 is the axial distance between the center Q of the guide grooves 2b and the joint center O, and the both are equal to each other.
Length PO3 of line segment linking center P of guide grooves 1b of outer ring 1 and center O3 of ball 3, and length QO3 of line segment linking center Q of guide groove 2b of inner ring 2 and center O3 of balls 3 are equal to each other, as indicated by PCR in
In this configuration, one (not shown) of two shafts to be coupled and outer ring 1 are connected, and other (shaft part 5) and inner ring 2 are connected. When the outer ring 1 and inner ring 2 form a certain angle, the balls 3 guided in the cage 4 are maintained within a plane perpendicular to a bisector of angle θ formed by the outer and inner rings 1 and 2, and therefore the distances PO3 and QO3 from the ball center O3 to the guide groove centers P and Q are equal to each other (PO3=QO3=PCR), so that the constant velocity of the joint is assured.
As described above, the offset amount (F=PO=QO) of the guide grooves 1b and 2b is set in range of value R1 of ratio F/PCR of 0.069≦R1≦0.121, and it is preferred from the viewpoint of assuring the allowable load torque, assuring the cage strength, assuring the durability, and assuring the working efficiency, and in this embodiment, the ratio is set at R1=0.104 (or 0.1038). In a comparative example (fixed type constant velocity universal joint of six balls as shown in
Referring back to
Supposing the wall thickness of the cage 4 to be A and the radial displacement of the ball 3 in one revolution of the joint to be B, the wall thickness A of the cage 4 is defined to satisfy the range of 0.45≦B/A≦0.65 in the BJ type, and satisfy the range of 0.65≦B/A≦0.85 in the UJ type. The optimum value range of wall thickness of cage differs between the BJ type and UJ type because, as already explained in relation to
The meaning of this numerical value range is illustrated in
Thus, in order to satisfy the both important properties of cage strength at high angle and joint durability at high angle, an optimum wall thickness setting of the cage is required, and the range is as specified above (0.45≦B/A≦0.65 in the BJ type, and 0.65≦B/A≦0.85 in the UJ type).
Claims
1. A fixed type constant velocity universal joint comprising:
- an outer joint member having eight arcuate guide grooves extending in the axial direction in an inner spherical surface thereof,
- an inner joint member having eight arcuate guide grooves extending in the axial direction in an outer spherical surface thereof,
- eight balls disposed between the guide grooves of the outer joint member and guide grooves of the inner joint member, and
- a cage interposed between the outer joint member and inner joint member for retaining the balls,
- wherein center of guide grooves of the outer joint member is offset from center of inner spherical surface, and center of guide grooves of the inner joint member is offset from center of outer spherical surface by equal distance (F) to opposite sides in the axial direction, and
- wherein the relation of 0.4523 B/A≦0.65 is established, where A stands for the wall thickness of the cage, and B the radial displacement of balls at maximum joint angle.
2. A fixed type constant velocity universal joint comprising:
- an outer joint member having eight arcuate guide grooves extending in the axial direction in an inner spherical surface thereof,
- an inner joint member having eight arcuate guide grooves extending in the axial direction in an outer spherical surface thereof,
- eight balls disposed between the guide grooves of the outer joint member and guide grooves of the inner joint member, and
- a cage interposed between the outer joint member and inner joint member for retaining the balls,
- wherein center of guide grooves of the outer joint member is offset from center of inner spherical surface, and center of guide grooves of the inner joint member is offset from center of outer spherical surface by equal distance (F) to opposite sides in the axial direction, and inner spherical surface of the cage is offset from outer spherical surface thereof to the opposite side by equal distance (f) in the axial direction,
- wherein straight portions having straight groove bottoms are provided in guide grooves of the outer joint member and inner joint member, and
- wherein the relation of 0.65≦B/A≦0.85 is established, where A stands for the wall thickness of the cage, and B the radial displacement of balls at maximum joint angle.
3. The fixed type constant velocity universal joint of claim 1, wherein value R1 of ratio (F/PCR) of offset amount (F) to length (PCR) of line segment linking center of guide grooves of the outer joint member or center of guide grooves of the inner joint member and center of balls is specified in a range of 0.069≦R1≦0.121.
4. The fixed type constant velocity universal joint of claim 2, wherein value R1 of ratio (F/PCR) of offset amount (F) to length (PCR) of line segment linking center of guide grooves of the outer joint member or center of guide grooves of the inner joint member and center of balls is specified in a range of 0.069≦R1≦0.121.
5. The fixed type constant velocity universal joint of claim 1, wherein contact angle of guide grooves and balls is in a range of 29° to 40°.
6. The fixed type constant velocity universal joint of claim 2, wherein contact angle of guide grooves and balls is in a range of 29° to 40°.
Type: Application
Filed: Sep 1, 2004
Publication Date: Apr 14, 2005
Patent Grant number: 7258616
Inventors: Masazumi Kobayashi (Shizuoka-ken), Tohru Nakagawa (Shizuoka-ken), Tomoshige Kobayashi (Shizuoka-ken), Masamichi Nakamura (Shizuoka-ken)
Application Number: 10/931,207